1. Field of the Invention
This invention relates to apparatus for driving the armature of a battery operated driver, such as an electric stapler, an electric nailer or other power tool to discharge a staple and, more particularly, to such apparatus which rapidly operates in succession, utilizes a minimal amount of external power, and automatically reverts to a quiescent mode within a predetermined time limit after being armed, but not activated.
2. Description of the Prior Art
Electrically powered staplers utilizing a solenoid armature or other electromechanical device for ejecting staples typically are powered by alternating current. As such, these AC powered staplers are plagued with problems associated with power fluctuations in the AC supply lines which result in performance problems including "double stapling" and/or incomplete stapling. To minimize the occurrence of these problems various voltage regulating and control means are employed including full or half wave rectifiers, Zener diodes and SCRs.
D.C. powered staplers utilizing similar solenoid armatures generally do not suffer from problems dealing with fluctuating input voltage, as in A.C. powered staplers. However, D.C. staplers rely on batteries and exhibit the problem of power consumption. Hence, such staplers require a design which minimizes the amount of power consumed thereby so as to increase the effective operating life of the battery. Ideally, an effective design would minimize both the power required to drive each staple and the power drawn while the stapler "waits" to drive a subsequent staple. Conventional D.C. powered stapler designs have failed to provide such a design.